Transformer-core.



PATENTED JULY 23, 1907.

W. A. HALL. TRANSFORMER CORE.

I lnveni'or,

Walfer' A. Hall. by Q Afi'y.

. Fig.4.

' Winesse= UNITED vsir. i'grrss ATENT OFFIQE.

WALTER A. HALL, or LYNN, MASSACHUSETTS, ASSIG-NOR To GENERAL ELECTRIC COMPANY;

.A ooeromrrou or NEW YORK.

-- .nnnnsronmnn eonn.

' To all whom it may concern: Be it-known that 1, Written A. HALL, a citizen of the United, States, residing at Lynn, county of Essex, State oi Massachusetts, have inventedcertain new and useful Improvements in Tr'ansformer-Cores,- of which -the following is aspecification.

-This inventionrelates-to electric transformers and its object is to improve the construction of the core, so that the transformer may have a large cross-section oi minilnurn mean length turn'oi copper.

iron with a small length of magnetic circuitfior the Q Theprcsent invention is a developlpent of that show and described-iii m y p tentaNo. 755,766 dated March 29, 1904. In that patent, the central leg of the core is cruciform in section, and two oithe. outside legs are ider than the other'two.

In my present invention, the central leg'is squarein cross-section, and all the outside-legs are of the same size as each other though each is smaller than the cen- .;.sec ti on in the outside legs than in the central -1 eg,.in order to lessen the reluctance of the magnetic hircuit outside-the coil and thus compensate for the necessa- 1 rilyjgreatcr flux density in thecentral leg.

,In the accompanying drawing-,Figure 1 is a perspec tive ew of one form of my improved transformer reinovedirom the casing Fig.2 is a transverse section of v number meeting at a central point. .Each branch is composed of sections, and each section is built .up of siniilzir ll-shaped laniinations. {in Figs. 1 and 2 three sections aroused for each branch. One of said sections it composed of stampings 1 having both legs of equal width but of different lengths: the laminations being-laid up with long and short legs alternating, in

the usual manner. The other sections b, c, are alike,

eachgboing built up of stam'pings 2 3 having one leg of the same width as the legs of the stamping l, bulf'tho other leg only halt as Wide. The stamping '2 has the widegleg the longer, While in the stamping 3, the narrow leg is the longer, so that when laid up alternately with the narrow'legs coinciding, there will he the usual spaces for interleaving the end pieces a. Each section is coniposed of the same number oi' laminations, and its thickness is equal to the Width of the narrow leg of the stamping-s 2 3. in forming the section, the -proper number of laiuiuntions are laid'togcthor, pressed in a powerful hydraulic or other pre s, and secured" in their compressed condition by LLELHSVQI'SO fiher rivets. I When the sections a, b, c are assembled to form a speciieation oi Letters Patent. fljdpplioation'filall September 24,1904.. Serial No. 226,736.

Patented may 23, 1907.

branch, they are laid with their widelegs coinciding.

The section a therefore projects beyond the other two along one edge by annmount equal to the difference in sections; thatis, equal to the width of and narrow leg. This forms a longitudinal rib or tongue'5 along one edge of each branch that is square in cross section. Adjacent to therib is a shoulder in shoulders formed by the edges of the sections b c. 1 n this form of my invention the section a is-between the-sections b, .6 so that there is a shoulder oneach side of the rib, of the same thickness as said rib. When theribbed edges of the several branches are brought together and interrneshed, each rib 5 abuts against one side of another rib, and is received between the shoulder of section b on one branch and the end of the rib 5 on the opposite branch. The shoulder of section 0 abuts against the side of the section b inthe next branch. In this case there is formed a substantially solid square central core leg, on which the coils 6 are placed. The central leg, portion of the core is thus formed of-four similar parts each composedoi a central layer oi laminae placed between a'pair of outer layers of lamimn. The laminae in the central layer, being wider than those inthe outer layer, project by the outer layers to form a rib' 5. One corner oi i'ach rih lies at the center of this square leg. The central planes of the branches are therefore all offset from the center of the leg by an amount equal to one half tlic'thickness of said rib. I

The cross-sectional area of the portion oi'tho section a forming a part of the center leg of the core is twice hat of the cmss-sectionalarea of the corresponding ortions of the other sections in eachln'anch, while the rose-sectional areas of the secthms in the remainder the branch are equal or substantially so. In conse oncnce, theportion of the section (1. in the central leg of the core carries more flux than Qitllcl' oi the cmre sponding portions of the other sections. This causes a certain ainount ot' flux to pass from tln cctimlsvband r: into the section a at one end oi the from the section a into the sections b not the other end of the central leg. By making the portion oi each branch entering the central leg 'synnnetr'rdal, with the section. a between the sections l) ande, the reluctance in the path oi. this cross-flux becomes quitesinall.

In '1 lgs. 1 and 2, the thickness of the branch is three fourths the width of the centralcore-leg. I1. is therefore necessary to make the outenltgs of the core of consideiable width, what may be called a radial direc- 1 log and greater. The object of this is L0 enable-tho outer and longer portions of the core to'operate at a flux density much below that portion inside the coils.

Now it is evident that by increasing the number of sections in each branch of the core, the thickness of said branch will more nearly approach that of the central leg, and consequently the width of the outer leg of the branch may be lessened, and thus shorten the magnetic circuit;

In Fig. '3 is shown a construction in which each branch is composed of five sections, all having one wide outer leg, one section a having a wide inner leg, two sections (1 having inner legs of two thirds the width of the sectiona, and two sections e having inner legs one third of said -width. The thickness of each section equals the width of the narrowest legs. The sections, are assembled preferably with the wide section a in the middle, and the others on each side, forming a double shouldered or stepped edge. The thickness of these branches is five sixths that of the central leg formed by intermeshing them as shown in Fig. 3.

The increase in the cross section of the external ma netic circuit by using wider legs is limited by the fact that there is a critical point beyond which any increase in width causes an actual loss in cost efficiency. In order, therefore, to increase the cross section without increasing the length of the magnetic circuit, thelaminatione may be spread apart in the outer legs, and additional sheets slipped in between them outside'the winding space, as shown in Fig. 3. This makes the outer legs thicker than the inner ones and materially reduces the flux density in the external circuit. I

These improvements have been found in practice to effect a large saving in cost and give a better electrical efficiency. v

I do not claim broadly as my invention a transformer core composed of units or parts'whosemeeting edges have longitudinal ribs which intermesh to form a substautially solid leg surrounded by a transformer wind ing, which construction I believe to be the invention of Claxton E. Allen. 7

What I claim, as new and desire to secure by Letters Patent oi the United States, is: Y

1. A transformer core composed of separate branches whose meeting, edges have longitudinal ribs which inte'rv illl'Sll to form n substantially solid leg, the rib on each branch being symmetrically disposed with respect to the central plane of said branch.

2. A transformer core composed of separate branches whose meetin' edgcs have longitudinal rlbswhicl are square in (l eciion, the rib on each branch being syminctl'icniLy disposed with reference to the central plane of Nil irl branch.

3. A transformer core composed 01 separate branches, each of which consists in part of sections each having one narrow and one wide leg, and in part of another section placed between the first mentioned sections and having two legs of the same width.

4. A t I'nsformer core composed of separutebranches, each of avhlch consists in part of sections each having narrow and wide legs, and in part of one section having legs of the same width, said. one section being placed between the ilrst mentioned sections, and the thickness oi? each section being equal to the width of the narrowest center, the central plan of each branch being elf-set from said center, and each rib being symmetrically placed with reference to the central plane of the branch of which it forms a part. I

8. A transformer core composed of branches having inner and outer legs, the former-intermeshed to form a central leg, and the thickness of the outer legs being -i-nner and outer legs, the former being shouldered and intermeshed toform a. central core-leg, and the latter having additional iron added to them to increase the crosssection of the external magnetic. circuit. 1

12. In a transformer, a core composed of branches having inner and outer legs, the former being lntermeshed together to form a central core leg, and each comprising a layer of wider laminae placed between g pair of other layers of narrower laminae, and a winding surrounding said central core leg and being, surrounded bysaid outer legs.

13. In a transformer, a core composed of branches having inner and outer legs, each inner leg comprising a layer of wide laminae between a. pair of layers of narrow laminae, said inner legs being interlocked together tofornia central core leg, and the outer leg having additional'lamime interleaved in them to make them thicker than the inner legs,

'andi). winding within said outer leg and surrounding said 

